On these pages, Joan provides practical advice on all aspects of designing, planting and caring for gardens throughout Santa Barbara, the Central Coast and the state of California. Visit her website at www.SantaBarbaraGardens.com.

June 27, 2012

Build Your Own Raised Vegetable Beds

A series of weathered redwood beds allows for intensive planting of summer vegetables, including Serrano peppers, tomatillos, eggplant, red bell peppers and two dozen tomatoes. These beds are spaced 3 feet apart to allow crops to spill over the sides, and to provide room for pushing a wheelbarrow in between.

Do your summer vegetables need a lift?

Raised beds are an excellent way to amp up your harvests.

Few of us have naturally occurring vegetable quality soil. It can be tough to create the rich, loamy stuff in the ground. Instead, start fresh, by building up.

An elevated growing space makes it easier to improve your soil’s fertility and tilth, and to water, weed and harvest crops.

With a few modifications, raised beds protect against rabbits and rodents. You won’t step on productive soil or waste it between rows. You can garden more intensively. And you’ll quickly find that raised beds are easy on the back.

The Basics

UC 157 asparagus, a perennial crop, will flourish for up to 20 years in a raised bed.

A traditional, stripped-down version is a rectangular wood frame with four posts.

The wood is typically redwood or cedar, although you can get creative with materials. For instance, stone beds are beautiful. But they’re pricey and their thick sides require more space.

Given a standard board length of 8 feet, 4 x 8-foot beds are a common size. That width is great for larger, perennial crops, such as asparagus, blueberries and raspberries.

But I think it’s too wide for seasonal edibles, including tomatoes, beans and peppers. You’ll be tempted to plant three rows. But the middle row will be nearly impossible to reach once the veggies gain size. Beds that are 3 x 8, with two rows each, are easier to manage.

The ends are nearly complete.

As for height: the boards should be at least 1 foot tall and 1 to 2 inches thick. A single, foot-wide board for each side is the simplest approach.

However, to save money, you can stack several narrower boards.

Just be sure the boards are straight and flush, so that soil and water don’t leak out between them.

Just one side to go!

Use sturdy 4 x 4-inch posts. Cut them 1 foot taller than the height of the bed, to allow for 1 foot to be buried in the ground. If you build a 1-foot tall bed, you’ll need four 2-foot lengths, or one 8-foot post.

Use long wood screws, rather than nails, to connect the boards and attach the posts. Angle brackets at each corner will provide extra stability.

Build your frame upside down on a flat space, such as a driveway or patio, with the posts in the air.

Prepping the Space

Carrots love crumbly soil.

Summer vegetables need at least six to eight hours of direct sunlight a day, while winter vegetables need at least four to six hours.

Mark where the raised bed will go, then excavate a foot of soil. Set the frame in place and level it.

The wood should rest on the finished soil level, rather than be buried, which will hasten deterioration.

Line the cavity with quarter-inch or half-inch aviary wire or chicken wire to thwart gophers, moles and other tunneling varmints. Bend the wire up against the interior sides of the frame, then secure the edges with a staple gun.

Also break up any dirt clods in the excavated soil.

The finer the texture, the more easily your edibles can gain a toe-hold in the bed.

The Soil

The beauty of a raised bed is that you have total control. The soil should be deep, fertile, hold moisture and drain well. It should smell fresh and sift easily through your fingers.

All done, and filled with a rich, sift-through-your fingers mix of topsoil, existing soil and redwood compost.

How much? A 3 x 8 bed, 1 foot tall and filled to the brim, requires 24 cubic feet of material. But your soil won’t go all the way to the top. Eighteen to 20 cubic feet is sufficient.

If your garden soil is free of weeds and reasonably loose and fertile, go ahead and “harvest” some.

But at least two-thirds of what goes into your raised bed should be high-quality soil builder, compost and/or topsoil.

Specialty products, like chicken manure and kelp, should be one-third or less. Do not use potting soil. It’s expensive and settles significantly.

Packman broccoli and green onions are flanked by orange calendulas in this raised redwood bed. After harvest, I’ll reinvigorate the soil by mixing in several inches of compost.

That new redwood bed replaced an old one in the same spot, so we used the soil from the old bed as a main component in the new one. And that soil was nearly 20 years in the making, with adding compost, compost and more compost every time we planted a new crop.

So have your rabbits passed from the adorable/cute phase to all-out menaces?

And will they pole vault over the bricks to eat your herbs, or are the bricks tall enough to keep them out?

Hey! Those illustrations look just like our beds — or like our beds used to look when they were new. Building them is just about my entire contribution to our gardening. Thank goodness for wives who garden.

I love my raised beds. Built the first ones almost 30 years ago. Quickly learned our sandy loam was one big playpen for every gopher and mole in Santa Barbara. Solved that problem by putting Aviary netting on the bottom of the beds. The beds have been rebuilt in recent years as well as the Aviary
replaced due to rust. No gophers or moles but have loads of rabbits to share. Anyone want some wild rabbits?

Sounds like you and Lydia truly could start a soccer league with your rabbits!

But seriously — have you tried any of the liquid or granular repellents? We’ve started a new program of cycling through three different products to keep our deer from devouring our plants. So far, it’s working well. I think most, if not all, of the products are listed as repelling rabbits, too.

Our soil isn’t worth excavating and using so I just built up. Not having enough soil, I went with the “no-dig bed” method. A layer of twigs, then flakes of good alfalfa, a sprinkle of blood meal, a layer of purchased compost (3″ or so), a layer of fluffed straw (6″ to 8″), a sprinkling of other nutrients such as bone meal and superphosphate and green sand, then another layer of compost. Wow, plants just jump out! You can use this method even on a cement patio. By the next season tho, half the volume has gone, been made into nice compost. You can refill with soil or a mix of soil and more alfalfa/straw and nutrients. Some of my beds are pretty tacky . . . free lumber stacked and held together with wire or metal posts . . . but the higher the better to keep out varmits! (rabbits may play soccer but I don’t think they jump up). On lower beds I’ve encircled with old poultry fencing or that plastic green fencing with holes in it . . . keeps our wild cat from using as good pee ground. The towhies and quail drive me crazy with their digging in the mulch for seed and bugs. I’ve kept bird netting on, but every year lizards end up getting strangled. Last year 2 snakes got caught; one I was able to cut out but the other had already died. This year we had to rescue a snake that got tangled in a roll of bird netting I got rid of from the garden but my husband put it on crossbars under the ping pong table (I had it on top pending a better place) and a piece fell low enough to catch it. I HATE bird netting! Finally bought some premium smaller hole net which is working well for the blueberries and blackberry, but it’s too pricey to do the whole garden . . . .

Wow! That’s ambitious! And interesting that there’s no actual soil in your initial setup. But it certainly seems to be working well for you.

At least one snake has been snared in our bird netting, too. What we now do to prevent that is drive the tips of a series of 4″ nails into all four sides — near the bottom — of a raised bed. Then we hook the bird netting onto the protruding nails and cut off the excess to prevent the netting from pooling on the ground. That way it’s not as likely to catch critters. Plus it’s a lot easier to lift the netting to tend to and harvest the veggies, then re-secure afterwards.